The present invention relates to a water treatment method and a water treatment apparatus, and specifically relates to a water treatment method and a water treatment apparatus used for pretreatment of treatment water where micro/nano bubbles are efficiently generated. Further, the invention relates to a water treatment method and a water treatment apparatus which are capable of greatly enhancing the efficiency in waste water treatment by introducing treatment water, which contains micro/nano bubbles, into a water treatment apparatus following the pretreatment apparatus, so that the water treatment apparatus is made compact as a whole and that the treated water quality is improved.
For commonly-used pretreatment methods and pretreatment apparatuses, there have conventionally been several kinds of water treatment methods and water treatment apparatuses.
As an example, there has been a pretreatment apparatus for biological treatment which performs settling, filtration, pH adjustment, ozone oxidation, adsorption and the like.
The purpose of providing the pretreatment apparatus is to reduce biological, chemical or physical loads for the subsequent-step water treatment apparatus. Thereby it can be expected to achieve downscaling of the water treatment apparatus, reduction in running cost, improvement of water quality in the treated water from the water treatment apparatus, and the like.
Meanwhile, JP 2004-121962A describes the method and apparatus using nano bubbles as a prior art.
This prior art utilizes such characteristics as reduction in buoyancy of nano bubbles, increase in the surface area, increase in the surface activity, generation of local high-pressure fields, and surface activation and bactericidal action by implementation of electrostatic polarization. More specifically, JP 2004-121962A discloses that interrelation between those characteristics makes it possible to lead to various functions such as an adsorption function for dirt components, a high-speed cleaning function for object surfaces, and a bactericidal function. As the result, various objects are cleaned under the high functions and low environmental loads, so that polluted water is cleaned.
JP 2003-334548A describe a nano-bubble generation method as another prior art.
JP 2003-334548A discloses that a method including the steps of (1) transforming part of liquid into cracked gas and (2) applying ultrasonic waves in the liquid, or (3) transforming part of the liquid into cracked gas and applying ultrasonic waves in a liquid.
In the field of water treatment using micro/nano bubbles, it has been desired to efficiently and stably generate micro/nano bubbles in water.